Glossary

ACTS (Advanced Communication Technologies and Services)

A European Commission research and development funding programme including digital broadcasting and next-generation Internet. Projects were as follows:

  • Motivate: Mobile Digital Terrestrial Television.
  • Crabs / Cabsinet: next generation LMDS for broadband local loop connection at 40GHz
  • iTTi: Return Channel for DVB-T.
  • MoMuSys: mobile multimedia systems.
  • Diceman: using new technologies to exploit AV archives.
  • CustomTV: MPEG4/7 object based interactivity over MPEG2 transport streams.
  • STORit: Use of local hard disc store to enhance functionality in home entertainment systems.
  • Infobridge: Promotion and dissemination of information from the ACTS projects

ACTS has now finished and future work in this area continues under the IST framework programmes.

ADSL (Asymmetric Digital Subscriber Line)

Invented by US company Bellcore (now Telcordia Industries) in 1989. ADSL has greater bandwidth in the forward path than the return path. It uses existing copper twisted pair local loop—its main advantage is the ability to roll out broadband to the home without digging up the pavement again. Crosstalk fundamentally limits the distance from the exchange it can work at a given bandwidth. 2Mb/sec is the calculated limit to reach 80% of existing connections.

It is an essentially different way to provide broadband connection to the method employed in cable modems—fundamentally it allows several users in the home to access the available bandwidth simultaneously whereas, with a cable modem, you need a second subscription for a second service. Likewise, this sharing of capacity is also an important feature to the telco operator which may become significant when local loop connections become extensively used for broadband applications.

The ADSL Forum is the industry group which is working to further development. It is estimated that there are about 100,000 existing ADSL connections in the world at this time but with consumer chipsets now in volume production, this is expected to grow very steeply in the next few months and years.

AFD (Active Format Descriptor)

Signal transmitted in UK DTT to ensure various types of letterbox picture are displayed to best effect on both 4x3 and 16x9 television sets.

(More: Tutorial on Active Format Descriptor)

Anamorphic

16x9 Anamorphic.

Used to differentiate a 16x9 widescreen picture which fills the whole frame, from a 16x9 letterbox with blank lines at the top and bottom of the frame. The Americans don't understand anamorphic in the context of television—their equivalent term is 16x9 full frame.

API (Application Programme Interface)

The Application Programme Interface is the operating system which provides the EPG and interactive functions in the digital receiver. It is the equivalent of Windows in a PC.

Existing proprietary APIs such as MediaHighway and OpenTV have fought a battle for the same dominance that Windows achieved but the tide has turned in favour of an open standards API. Many people believe that should be MHEG-5 and Canal+, the owners of MediaHighway, have committed to changing over to it. But MHEG-5 is an anathema to the Americans. The common denominator for the future is Java and this has now been adopted by the DVB Project for their Multimedia Home Platform development. MHEG-5 and other existing systems will become plug-in classes to a Java Virtual Machine.

ATM (Asynchronous Transfer Mode)

ATM stands for Asynchronous Transfer Mode and is a method that is taking the telecom industry by storm for splitting digital audio, video or data signals into little data packets, which can all be fed together into ginormous bitstreams and, with luck, reach their right addresses and can be put back together in the right order.

BAT (Bouquet Association Table)

An optional element of SI which provides a means of pointing to associated services on other multiplexes.

BlueTooth

In-home radio system for communicating between devices in the same room. It first appeared in mobile phones and linking computers and peripherals wirelessly, but you will soon be using your mobile phone as a remote control for the telly—Bluetooth is going places according to the advocates.

The name, incidentally, is that of an ancient Scandinavian king.

The Blootooth want prices to fall to $5 a chip by 2003. Research suggests the market in devices rising to $400m in 2001 and $5bn by 2005.Arc Internationaal is amongst the leaders in the technology with a design based on its 32 bit Tangent processor. The company claim its implementation is smaller, cheaper and lower power consumption than rivals.

Could it be a means of communicating between devices in a home entertainment system? We its currently nowhere near fast enough for video and Hiperlan is the favourite. But who knows?

CA (Conditional Access)

A means of allowing system users to access only those services which are authorised to them.

(More: Tutorial on Conditional Access)

Centre Cut-Out

One of the ways of viewing widescreen programmes with an existing 4x3 television set and a set-top box. A 4x3 patch is taken from the middle of the 16x9 image, with considerable cropping of the image at the side.

The digital set-top box or tv set has a capability for pan-vectors, such that the displayed patch can follow the action, but it seems unlikely that broadcasters will programme pan-vectors except, perhaps, for a few prestige programmes. However, broadcasters will compose widescreen pictures knowing that many people will be watching in 4x3, so not too much action will be lost.

The alternative is to switch to a letterboxdisplay, where the whole image is seen but with black bars at the top and bottom. That is likely to be the best way to watch movies on tv. Second generation set-top boxes will probably offer a 14x9 compromise where there are small black bands top and bottom. But the best solution is to buy a widescreen tv!

(More: What is Widescreen?)

Common Interface

Connection for plug-in computer card in the receiver, designed to carry the conditional access subsystem. Its proposed use also includes plug-ins for audio description and much, much more.

In order to increase the usefulness of the Common Interface, seven extensions have been proposed and are on their way to adoption by DVB. ONdigital are committed to developing the MediaGuard CA sytem on a module for use in Open Standards idTVs and making use of the common interface extensions. Unfortunately, the extensions will delay the module until the second quarter of 1999, which is too late for at least three manufacturers. So an interim 'classic' module will be issued to early purchasers.

Control Word

The secret key used for a scrambling algorithm.

(More: Tutorial on Conditional Access)

Convergence

Convergence denotes the coming together of diverse communications technologies so that they no longer have unique associations with particular types of service.

  • Radio and television broadcasts can be delivered to the home by cable instead of through the ether, but that same cable can also carry voice telephony and data.
  • Satellites can handle all types of telecommunications traffic, including broadcasting direct to the home.
  • The personal computer, when connected to a telephone line, becomes an audio- visual receiver as well as a data terminal.
  • The Internet has a capability for broadcasting as well as point-to-point data carriage, despite being accessed through the 'plain old telephone system'.
  • Radiotelephony, once a specialised and highly regulated technique, is now an everyday facility in the form of cellular mobile telephones. The wired telephone systems now carry services that were unknown in the days before liberalisation, and will be able to deliver many more as digital technology is extended.

Copy Protection

A system which allows live viewing of movies and other programmes but prohibits back-to-back copying. Particularly important in the new digital era since the quality of recordings is indistinguishable from the original. The system to be used is called Macrovision.

DAVIC (Digital Audio Video Council)

DAVIC is a worldwide association of bodies concerned to promote interoperability in audio visual equipment of all kinds concentrating on standardised interfaces. A major focus of their work has been an API for the set-top box and the DAVIC 1.3 API consists of an MHEG-5 content decoder with an additional cut down Java virtual machine.

DCT (Discrete Cosine Transform)

The Discrete Cosine Transform is the technique for getting at the redundancy which is in television images in order to reduce the datarate. It is a fundamental part of the MPEG-2 compression process.

DigiTAG

DigiTAG—is the European equivalent of DTG in the UK, being a consortium of broadcasters and manufacturers working on common standards within the DVB framework with the objective of achieving a European wide market for receiver designs. Digitag operates under the auspices of the EBU.

(More: DigiTAG web site)

DMux Group

DMux Group—the original name given to meetings of the four terrestrial multiplex operators, BBC, Digital3&4, SDN and ONdigital and now branded as The Digital Network.

DOCSIS (Data Over Cable Service Interface Specification)

DOCSIS is the physical layer and format protocols for cable modems in the USA and seems likely to be adopted in many countries helped, it must be said, by Microsoft's investment in cable companies in many territories. Unfortunately the DVB have their own standard just coming to fruition and it seems likely that both standards will be rolled out over the next few years.

The American standard was, in fact, submitted to the DVB for consideration earlier this year but the Technical Module was by then well advanced with its own, so DOCSIS did not find favour. So resolution of the problem passed upward to ETSI and the ITU. But really it was too late to look for a single standard with cable companies already implementing digital cable. Now higher authorities have a problem with schizophrenia. On the one hand, they, of course, want to see a single standard in place to benefit the industry and the consumer. On the other hand, they are all for competition and would seriously undermine their credibility if they took a partisan approach. So it is strongly rumoured that the ITU will adopt a standard which refers to physical and low level transport protocols layers as alternative appendices. It then will come back to the DVB to accommodate DOCSIS modems within the DVB framework.

Microsoft's bottomless piggybank is, of course, tipping the balance a tad, and the UK cable companies will go with MCNS / DOCSIS. But DVB modems are strongly supported elsewhere in Europe and there are likely to be half a million of them in circulation by the end of 1999. It only goes to prove the importance of getting technical standards in place ahead of the commercial need.

DSM-CC (Digital Storage Media, Command and Control)

The DVB defined method adopted for UK DTT for transmitting data in an object carousel.

DTG (Digital TV Group)

THE association of interested parties committed to launching digital services in the UK who's website you are now enjoying!

DVD (Digital Versatile (originally Video) Disk)

Data storage medium used, amongst other things, for distributing consumer video with a standard recording 4.7GBytes giving 140 minutes at an average of around 3Mb/sec, but with a peak capability of 8Mb/sec. It is this that digital broadcast TV will be compared to.

Dynamic Multiplexing

Variation of datarate programme by programme so as to allow simultaneous transmission of other services. Involves a calculated risk that shots within the programme will not exceed the allowed datarate.

ECM (Entitlement Control Message)

A component of the electronic key system (sometimes called the Multisession Key) and is transmitted encrypted to control the descrambling process. Its use has been perverted(?) by some satellite operators to carry specific programme pricing information. Jokingly said also to stand for Electronic Counter Measures.

EIT (Event Information Table)

Part of the SI which is used to transmit information about events (programmes) in the MPEG transport stream. The DVB mandate the transmission of details about the present and following events for the multiplex concerned; the ITC mandate the transmission of present-and-following for the other five terrestrial multiplexes; beyond that it is optional whether to use the EIT to provide comprehensive listings (ESG) or to transmit an EPG as privately defined data.

EMM (Entitlement Management Message)

Also known as Unit Secret Key, it authorises specific decoders to decrypt the broadcast service, programme-by-programme if required.

Enhanced Data Broadcast

An enhanced data broadcast is one which allows the viewer to select and view various pages of information but there is no connection to a remote server via the telephone or other return path.

Interactive data services build on this concept by adding the return path (sometimes called the back channel) by which the viewer may choose additional information or services.

EPG (Electronic Programme Guide)

The new flashy name for that part of what teletext currently does. In digital, it is possible to make the images a lot smarter than teletext.

BSkyB are making a great feature of their EPG and, indeed, usability is an important feature when trying not to miss a programme you want amid 200 channels. However, it uses a proprietary method of encoding and is difficult to separate from the secret bits of the conditional access system (because, of course many of the services are scrambled and, if you are not entitled, the aim is to let you see but not touch!)

In an effort to force some commonality between satellite and terrestrial, the ITC are proposing that both platforms carry a 12 hour schedule in the SI (service information), which all receivers could decode. Neither party is very happy with that and currently only propose to transmit the DVB mandatory now-and-next.

ESG (Electronic Service Guide)

The ESG is a basic navigation system resident in the receiver or set-top unit which uses programme schedule supplied by broadcasters in open SI. As such it is non-proprietry

ETSI (The European Telecommunications Standards Institute)

The body responsible for technical standards in television in Europe, which stands below the world standards authorities ITU and ISO

Firewire

Properly known as P1394. Serial digital bus connector for interconnecting domestic units, sometimes known of as firewire and ultimately likely to replace the function of the SCART socket in analogue. The proper name for P1394 is IEE High Performance Serial Bus. P1394 has been chosen by the DVB Multimedia Home Platform Committee for interconnection of digital equipments in the future home-area network. P1394 defines the physical layer—the transport layer is likely to be ATM.

GPRS (General Packet Radio Service)

Sometimes called 2.5 G, GPRS is the interim step in mobile phones between WAP and 3G. WAP has been an unequivocal flop with the European public because of slow access times, poor handset battery life and lack of interesting services.

GPRS should reduce access times from 20 secs or more to 3—4 secs. when it arrives in mid 2001. But network operators have a steep learning curve so it is unlikely to be brilliant at first.

HAVi (Home Audio/Video Interoperability)

We are fast approaching a time when users will find it necessary to be able to connect their digital AV appliances to create home entertainment networks. For different brands of AV electronics appliances to be interconnected and interoperated, each appliance must incorporate middleware that contains certain software elements common to all appliances on the network.

HAVi is an abbreviation for "Home Audio/Video Interoperability" and is a means of interconnecting and controlling AV electronics appliances in an in-home network based on IEEE-1394. The core specification was developed by a group of companies consisting of Grundig, Hitachi, Matsushita, Philips, Sharp, Sony, Thomson Multimedia and Toshiba following an agreement to work together in May 1988.

The core open home network specification defines these elements, their roles and their functions. In addition, it ensures that the software elements of different appliances will work together. The HAVi v1.0 specification and compliance test spec was published in January 2000 and the first demonstrations of the HAVi home network were made to members of the press and electronics industry at the CES show in that month.

The patent holders have announced a joint licencing process with the MPEG LA legal practice acting on their behalf. Since the formation of the HAVi Organization in November 1999, fifteen companies have become members. These companies include Digital Harmony Technologies, Loewe, Kenwood, LG Electronics, Mitsubishi Electric, Pioneer, Samsung Electronics, Sanyo, Seiko Epson, Sun Microsystems, Tao Group, QNX Software Systems, Vivid Logic, Wind River Systems, Yaskawa Information Systems. A large number of other organizations also have expressed their support for HAVi, or their intention to become a member.

(More: HAVi web site)

Hotspot

A graphical box or other object on the screen that the viewer can interact with.

HTML (Hypertext Mark-up Language)

HTML is the language of the web. It consists of blocks of text and images with embedded instructions on how it is to be presented by the browser. HTML has the ability to embed hypertext links to other HTML files, either on the same site or anywhere on the web. These URLs take the form of http://www .... The standards for HTML are under the control of the Wordwide Web Consortium (W3C), an open standards making body representing all companies with interests in web development.

What makes HTML of interest to digital television is the amount of content which is being created in HTML. Creating content costs money and costs can be amortised by reusing or reversioning content for Internet use, for CD-ROMs and for digital television. HTML based information could permit truly local news on digital television, could allow advertisers to link adverts to more information for use by interested viewers, etc.

(More: Wordwide Web Consortium web site)

Impulsive Noise

The term which describes the clicks from central heating boilers in the home, washing machines and light dimmers, which can cause a flash on analogue televisions in marginal reception conditions and, with digital reception, may cause blocking, freezes, and high pitched clicks on sound.

In many cases, the equipment causing the interference is illegal and should be replaced. However, it is not usually tactful for an installer to suggest that. The alternative is to improve the aerial installation by:

  • better earthing of the installation
  • external rather than loft aerial
  • quality twin screened downlead and especially the interconnecting lead from the wall

One particular form of impulsive noise is ignition interference from passing vehicles, which can be 'the straw that breaks the camels back' in marginal reception conditions. The improvements above will help but, in addition, try moving the aerial to the back of the house such that the roof provides screening from the road. Also, tilting the aerial upwards by perhaps 5 deg is also helpful. The problem can be made worse if the analogue signal levels are close to overload so the usual advice about minimum gain of pre-amps applies.

Many first generation set-top boxes employ MPEG decoder chips which are not very robust in this respect. It is likely that improvements will be made in this area in second generation equipments.

Interoperability

Interoperability is the holy grail of all multiplex operators. Digital set-top boxes are fearsomely complicated; specification and testing to ensure different types perform the same way is a big and expensive overhead at best and a potential nightmare in an open market situation.

In a closed system, the multiplex operator would expect to have a contract with its suppliers to provide comprehensive conformance testing. In DTT, responsibilities are not so clear-cut. The DTG could have a role to play.

IRD (Integrated Receiver Decoder)

Beware terms—integrated does not mean that the box is part of the display unit! Usually the term is now reserved for professional equipments used at cable head-ends etc.

IST (Information Society Technologies)

The European funding programme—part of the 5th and 6th (et al) frameworks for research and technology development—which took over from earlier programs such as ESPRIT and ACTS.

Java

An object oriented programming language developed by Sun Microsystems which is designed to be small, simple and portable across platforms and operating systems. It has come to prominance as an extention to HTML coding for the Internet. A cut-down version, dubbed personal Java, has great attractions as the virtual machine for the digital set-top box. and forms part of nearly all developments by API suppliers.

It has recently been adopted by the DVB Project for use in the multimedia home platform (MHP) standards.

Joint Stereo

A coding option in MPEG for exploiting the redundancy between left and right audio channels and transmitting at 192kb/sec. However, research suggest that this is not adequate when Dolby encoded surround sound is transmitted. As broadcasters don't always reliably know when feature films are Dolby encoded, it may be safer to transmit everything as separate stereo at 256kb/sec.

JPEG (Joint Picture Expert Group)

JPEG stands for Joint Picture Expert Group, which preceded MPEG. It dealt only with still pictures but the standard was adapted and adopted widely for moving images—so-called Motion JPEG or M-JPEG. The snag is that one manufacturer's Motion JPEG decoder probably won't read another's signal correctly.

Letterbox

A television picture with blank lines top and bottom giving an aspect ratio of either 14x9 or 16x9 or occasionally wider. However, as not all of the tv lines are used, the pictures have reduced resolution on a widescreen tv compared to true digital widescreen.

(More: What is Widescreen?)

Macrovision

Copy protection is a system which allows live viewing of movies and other programmes but prohibits back-to-back copying. Particularly important in the new digital era since the quality of recordings is indistinguishable from the original. The system to be used is called Macrovision.

MHEG-5

In the argument over APIs, it is often said we should adopt HTML as so much content is mastered in HTML. However, HTML is designed for a different purpose and fundamentally does not allow the placement of text and objects on the screen in a predictable way. MHEG-5, the core of the DAVIC API, does the job properly (and can take HTML as its source). DAVIC V1.3 (though not the Java virtual machine) has been adopted by the terrestrial multiplex operators as the UK 'Content Decoder.'

MOTIVATE (Mobile Television and Innovative Receivers)

EC funded ACTS project established in 1998 to investigate the practical and theoretical limits of DVB-T mobile reception.

The project partners were:

BBC (UK), Bosch (D), Berkom (D)*, CCETT (Fr), EBUIRT (D), ITIS (Fr), IRT (D), Mier Comms (Es), Nokia (SF), Nozema (NL), RAI (It), Retevision (Es), R & S (D), TDF (Fr), Televés (Es), Teracom (S), Thomcast (Fr)

* Project Coordinator

Motivate is investigating different network structures (MFN, SFN, gap-fillers, microcell / macrocell, etc to produce an optimised network topology, also considering appropriate modulation factors /code rate /guard interval to produce a reference receiver model for planning purposes and implementation guidelines. Early results show the advantage of 2K carriers for mobile reception and the advantage of QPSK or 16QAM modulation for robust reception. Appropriate parameters depend on the maximum speed assumed for the vehicle (for example reception on a high speed train would dictate lower datarates than, for example, urban public transport). Code rate 1/2 appears to be a sensible limitation for speeds up to 100km/hr. Work is proceeding to broaden and confirm findings, investigate hierarchical coding and optimise network topologies.

Now moving from research into exploitation, the best example of its use was at IBC '99 where No 4 trams from Central Station to the RAI exhibition halls in Amsterdam were equipped with 15-inch LCD screens showing live DVB-T transmissions.

MPEG-2

MPEG Stands for Motion Picture Expert Group, which co-ordinated the design of the family of standards that all digital broadcasting and DVD moving images employ.

The group's first standard was just called MPEG (later to become MPEG-1) which was designed to be used on narrow band systems like CD-ROMs and with a bit rate of around 1.5 megabits. It used progressive scan pictures.

MPEG-2 understood interlace and could use variable bit rate encoding for greater efficiency. It was aimed at broadcast quality systems running at around 5 megabits per second.

MPEG-4 was an object oriented system able to cope with elements of a scene, both vision and sound, as independent parts.It also included very efficient compression for low bandwidth systems such as mobile telephony.

MPEG-7 aims to standardise the metadata (as it is known) with which audio-visual information is labelled for indexing and archiving.

MPEG-21 is a new proposal covering all aspects of multimedia information.

Multiplex

A uhf channel that is used to carry digital signals. By means of compression, several services can be carried in the same channel. How many is the hot question.

Multiplex Operator

Broadcaster transmitting on one or more multiplexes. The UK digital terrestrial platform has four multiplex operators, BBC, Digital 3&4 (ITV and C4), SDN and ONdigital. ONdigital have three multiplexes; the others have one each. A multiplex operator may not be the originator of broadcast services—ONdigital, for example, take all of their programmes from other service providers. They operate the subscription services and pay the service providers for the programme services they provide.

Navigation

The process by which the viewer is able to find wanted programmes in the multi-channel situation.

NIT (Network Information Table)

One of the four mandatory Service Information tables transmitted with every digital broadcast to identify itself.

Now and Next

Slang for the present and following events in an Event Information Table.

NVOD (Near Video on Demand)

Technique used in digital Satellite and Cable services using several channels to transmit a feature film with staggered start times.

If you are anything like me, the one thing you can bank on is that BBC, ITV, Channel 4 and 5 for that matter, will start their feature films at an inconvenient time (to me). For example, Channel 4 features are a lost cause, because my mum told me most severely before I left home that I must be in bed by eleven. I try to use the video but I either forget to program it or it gets lost with all the others that I failed to label! So, if Saturday night viewing looks awful, we call by the video store on the way home from shopping. Thats good, because we can press the play button when we want to.

Now, all this is not lost on broadcasters fighting for every percentage point rating and digital compression offers the tools to fight back .... near-video-on-demand or NVOD for short. The principle is simple. If you've got more channels than you know what to do with, why not use a block of, say, six of them to play the film with staggered start times. That way your viewer is never more that 20 mins away from the start of the film whenever he (or she) sits down. And that is the way you'll see it on Sky Movies or Front Row on cable. But not, unfortunately, on DTT—alas, poor dears, they don't have enough bandwidth for NVOD.

ODFM (Orthogonal Frequency Division Multiplex)

The method of taking thousands of tiny carriers to convey digital signals in a spectrum that is already full of analogue ones. The equivalent method of modulation for satellite broadcasting is QPSK and for cable is 64QAM.

P1394

Serial digital bus connector for interconnecting domestic units, sometimes known of as firewire and ultimately likely to replace the function of the SCART socket in analogue. The proper name for P1394 is IEE High Performance Serial Bus. P1394 has been chosen by the DVB Multimedia Home Platform Committee for interconnection of digital equipments in the future home-area network. P1394 defines the physical layer—the transport layer is likely to be ATM.

Parental Control

Ever since the 'V-chip' appeared to offer politicians a magic wand to protect our innocents from nasty adult television material, regulators have been chivvying broadcasters to do something about it. Broadcasters, meanwhile, have continued in their assertion that it is up to the parents to protect their young minds from filth and ensure that their offspring are in bed before the threshold of 9pm, when they reserve the right to start transmitting strong material.

This rather simplistic stand-off actually masks the fact that most broadcasters actually go to great lengths to preview programmes to identify potentially offensive material, and to provide warning of passages which may be seen as offensive in some circumstances, such as train crashes when there has been a real incident, etc.

Anyway, mindful of the pressures upon them, the DVB has assembled a panel of sympathetic regulators to consider the problem. Their report points out that a system that only applies to digital television would distort the market and not fulfill the requirement and they propose a new system for parental rating which should operate across all delivery platforms. The standardised descriptions would allow each consumer to avoid material which was personally offensive, acknowledging that what is considered offensive differs widely between countries, races and religions. A standardised system would be a help to programme providers and broadcasters and would therefore encourage its use.

The system proposed would be based on industry self-regulation but include methods to deal rapidly with any abuse of the ratings system. An 'unrated' category is also proposed to avoid imposing the burden of rating content where it was not appropriate (eg normal commercial websites).

The proposals will be submitted to regulatory authorities for their consideration.

Pause Point

A natural break in presentation where the aspect ratio can be switched without serious breakup or digital artifact. Black is best but it may be possible to switch on a still frame when the MPEG decoder buffer will be relatively empty.

Pay-Per-View

The alternative to subscription and isregarded by many to be the new source of income of the future, but essentially requires a return path.

Where large numbers of people want to subscribe to an event in the minutes before it starts, a system can be overloaded. Rather than entitle individual IRDs, it may be better to download credit to the smartcard and deduct from that as a local transaction, which is subsequently signalled to the SMS overnight.

PCMCIA

The computer plug-in card which has the same physical size as the Common Interface module and is plug-compatible.

POF (Plastic Optical Fibre)

Recent alternative to glass, it has the advantage that its diameter is much larger and therefore easier and cheaper to join than conventional optical fibres. Applications include automotive electronics and in-home digital networks using IEEE1394.

The Japanese Kobe University and Asahi Glass Company are acknowledged leaders in the field.

POTS and PANS

POTS is an acronym for Plain Old Telephone Service—what most people use for browsing the internet and for the return path for set-top box interactive services. As this is the main reason for people saying that www stands for World Wide Wait stand by for ........

PANS short for Pretty Amazing New Stuff. Attributed to Barclay Knapp, CEO of NTL, to describe the broadband services they and others will be rolling out over the next few years, with 2 MB/sec or more in the forward path allowing delivery of video on demand and really impressive internet services. Whether the servers will be up to it and who is going to pay for it (as if we didn't know) is the sixty four thousand dollar question!

Present and Next

Alternative form of Now-and-Next. Slang for the present and following events in an Event Information Table.

PVR (Personal Video Recorder)

The personal video recorder (PVR) is a result of the convergence of the broadcasting and computing technologies. PVRs exploit the compression techniques developed for digital broadcasting to squeeze useful amounts of television programming onto a computer hard disk of affordable size.

We have seen the amount of disk storage in PCs double each year for no increase in price: at the same time compression techniques allow a television signal originated at the 270 Mbit/s studio standard to be squeezed down to just 5 Mbit/s or so. Inevitably the point had come where a whole two-hour movie could be recorded on a low-cost disk 5Gbyte is more than sufficient. (A look at the Seagate website shows several 17GB disks available at less than E100 and the PVRs now on offer in the USA will store up to 30 hours of programmes.)Recording on disk is still more expensive than on a E3 VHS tape but it brings a number of benefits to the viewer:

  • Record and play at the same time Random access to recorded content
  • Variable playback speed

Translating these to consumer features, with a PVR you can:

  • Record one programme whilst watching a different programme Record a programme but skip back to watch a highlight again. If you miss a line of dialog, push the rewind button and listen to it again. The PVR will continue recording the programme while you pause to review the stored information. When you are ready to continue watching the programme, push the play button and the programme will pick up from where you left off. Start watching a programme from the beginning after it has started - no need for the agonizing decision when you have started recording your favourite Soap before you get home and can't decide whether to watch what's left of the programme or wait for the recording to finish!
  • Pause a programme that is being watched to answer the 'phone, make coffee or even look on the TV programme guide to see what else is on without losing any of the original programme.

Even with just these features, the disk-based video recorder looks attractive. But the manufacturers have gone further and made it Personal. By downloading programme schedules into the PVR they allow the viewer to select in advance what they want to record and watch. They go further and allow the viewer to rate the programmes they watch and some PVRs will learn your viewing habits over time: this information about personal likes and dislikes can then be used to present you with a list of suggested programmes that match your preferences. For their operation, the PVR needs to be fed with the programme schedules for all the channels together with information about each programme to enable its type (e.g. news, movie, sport) to be identified and some descriptive text for the view to decide whether or not to view/record it. The way in which the TiVo service achieves this is for the PVR to be connected to a telephone line and to dial up a database from which two weeks of schedules are downloaded to the PVR. There is a charge for this in the form of a monthly subscription or a lifetime payment.It doesn't take a genius to realise that a portal has been created through which viewers get access to their programmes. And just as with Internet search engines it is important to a broadcaster that his programmes get a prominent position in the listings. Not surprising, then, that the BBC has signed a deal with TiVo whereby in exchange for technical assistance the BBC will have prominent placement on TiVo's on-screen menus - called Channel Highlights in the UK and known to U.S. viewers as Network Showcases. The BBC Channel Highlights menu on the TiVo service will offer a themed selection of the best of BBC programmes and will allow viewers to easily select programmes for future recording.There is no doubt that the PVR is having a significant effect on the viewing habits of the 100,000 or so owners of TiVo and Replay PVRs in the United States. It is reported that TiVo-equipped households watch 3 hours more TV a week than other households - but they don't watch scheduled TV anymore. According to Josh Bemoff, a television industry analyst with Forrester Research in Cambridge, Mass., who closely follows the fortunes of TiVo and Replay, viewers "get into the habit of not paying attention to when the programs are on andjust watch what they've recorded." This means that the concept of "prime time" and the advertising revenues that go with it could become a thing of the past. Likewise, the viewer has become the schedule controller and clever packaging by the broadcasters will be less effective in retaining the audience. Increasingly, viewers' loyalty will be to programme brands rather than channel brands. It will be more difficult for networks to attract audiences to new programmes by launching them in prime time when everyone is watching: instead, each programme is competing for the viewers against all others whenever transmitted.There is worse to come. Those PVR owners don't watch commercials anymore. In a survey, eighty-eight percent of the advertisements in the programs delivered to viewers on their PVRs went unmatched. Advertisers and broadcasters alike need to find new ways of attracting audiences - we can see advertisements becoming more entertaining, more interactive and, probably, more targeted.

For broadcasters, the PVR offers an opportunity for new programming styles. Viewers can select the items from a magazine programme that interest them or can watch programmes in a non-linear way, just as some people read the sports pages of a newspaper first while others go straight to the financial pages). Drama programmes delivered specifically for later viewing could be segmented with options for viewers to follow one route or another through the story. And linking programme content to other applications could create a powerful leaming package.

David Bradshaw

RST (Running Status Table)

There is no requirement that the now-and-next EIT is synchronised with programme junctions. The RST is an optional element of SI which can be used, for example, to start a vcr.

Safe Area

A reduced area of the picture which should contain important action and graphics may be placed without fear of cutoff. With mixed 4x3 and 16x9 viewing, what is safe is a debatable point!

Scrambling

The process of making a signal unintelligible such that it can only be received if an authorised descrambling system is available in the receiver.

SDMI (Secure Digital Music Initiative)

A consortium of companies working on copy management aimed at stopping the illegal copying of MP3 files over the internet.

Chief Executive is Leonardo Chiariglione, the redoubtable Head of TV Technologies at CSELT, Telecom Italia's research centre. SDMI recently ran a "hack SDMI" challenge to see if four alternative approaches being studied were secure. A team from Princeton University claims to have hacked all four in a couple of man-weeks of effort, thus proving that you will never stop the determined burglar. However, breaking encrypted files this way is clearly illegal and, together with watermarking to identify the source, makes prosecution easier.

Meanwhile two code-breakers received cheques for $10,000 for their efforts in pinpointing weaknesses in the schemes.

SDT (Service Description Table)

One of the four mandatory SI tables which lists the names and parameters of each service referred to.

Service ID

A unique identifier of a service within a transport stream and part of the SDT.

SFN (Single Frequency Network)

A way of broadcasting from a grid of transmitters using only one frequency. Restrictions on transmitter spacing make it inappropriate for the UK.

Shoot and Protect

The buzz-word which describes framing pictures for display at more than one aspect ratio. Hollywood has been doing it for years—producing 4x3 tv versions from CinemaScope masters; protecting 4x3 viewers from 16x9 originals has to be a darn sight easier!

SI (Service Information)

The basic overhead in a multiplex transmission which tells the IRD what services it has and how to tune to them.

Signing

There are 70,000 deaf people in the UK who use sign language. The Broadcasting Act 1996 requires the signing of 1% of all programmes (15 mins per day) within 1 year of launch. This must increase to 5% within 10 years. Signing is defined in British Sign Language (BSL) but there are variations which can cause confusion.

Simulcrypt

The DVB has given its backing to two approaches to CA, simulcrypt and multicrypt. Simulcrypt is intended to permit different CA operators in different geographic areas. The service carries entitlement messages for each CA provider within an agreed common framework, but the viewer does not have a choice of SMS. In technical simulcrypt, the system is designed to allow two competing CA systems within an agreed framework. Multicrypt is an open system which makes use of the common interface to allow competing CA systems, subject only that the service provider must transmit entitlement messages for each CA provider.

SMC - SMS (Subscriber Management Centre - SMS Subscriber Management System)

The business centre which issues the smart cards, sends out the bills and receives payment from subscribers. An important resource of the SMS is the database of information about subscribers, the serial numbers of their receivers and information about their preferences and servics to which they have subscribed.

StatMux (Statistical Multiplexing)

Technique for varying the datarate shot by shot according to the needs of the picture. The multiplexer manages the allocation of datarate between services within a multiplex to give greater "bandwidth" where it is needed. Over a 36Mb/sec satellite multiplex, it is so effective that it is usually posssible to squeeze in extra services; with a 24Mb/s terrestrial multiplex, the gains are not so great but, at the least, the number occasions where compression artefacts become visible is reduced.

The problem with statux is that it requires close coupling between the multiplexer and its encoders. Thus, the technique cannot be used when a multiplex has regional variations, such as the BBC or ITV / C4 multiplexes. A different approach has to be taken. Pioneering work by BBC Research and Snell & Wilcox as part of the Atlantic project, amongst others, shows great promise but has not yet been put into practice.

STB (Set-top Box)

Receiver connected to a TV for display. More properly referred to as an STU—Set-top Unit!

TDT (Time and Date Table)

Mandatory data transmitted within SI to synchronise the receiver's internal clock.

TV Anytime

As with most new products, PVRs such as TiVo and Replay Networks are based on proprietary standards. that will not interoperate. There are other players entering the market with their own offerings, including Metabyte Networks (www.mbtv.com), Axcent Media (www.axcent.de). NDS/Liberate who have an agreement to make NDS' PVR technologies, including NDS' personalized TV product, XTV, and NDS Open VideoGuard© conditional access solution a component of the Liberate TV Platform software for set-top boxes with hard disks. All too easily we could have a number of proprietary closed systems competing for our cash and presenting the broadcasters with the problem of feeding all these portals with scheduling and descriptive information.In an attempt to avoid this situation and to enable PVRs to receive content from the Internet and Broadband as well by the more traditional delivery methods, an international Organisation was formed last year to pursue the development of open standards for PVRs and similar devices. Called the "TV Anytime Forum" (www.tv-anytime.org) it is working on specifications for content identification, descriptive metadata and - probably the most difficult area of all - rights management. The working documents of the Forum are available to anyone interested in contributing to their work; details are available from their website. Over 100 companies are members of the Forum.Contributing to the TV Anytime Forum's work is an EU-sponsored project, myTV, (www.extra.research.philips.com/euprojects/mytv/) which is all about personalised television and involves both manufacturers (Philips, Nokia, NDS) and broadcasters (BBC, RAI, NOB). The objectives of the myTV project are:

  • "to develop, standardise, implement, validate and demonstrate a consumer platform with built-in local storage, for personalised services in digital broadcasting and broadband communication. This platform will enable consumers to have access to content and services at their convenience, independent of the moment of broadcasting.
  • to develop new services exploiting this platform. Appealing examples include the ability to turn local storage into a personalised television channel, non-linear browsing of television content, interactive and targeted advertising, and easy navigation through the massive amount of content offered.
  • to provide true interoperability, both across different service providers and across different box manufacturers. Therefore contribution to and adherence to standards is another important objective of the myTV project."

It is probably not unreasonable to expect the development of the DVB-MHP specifications to embrace both Internet interfaces and integrated storage in the near future.

David Bradshaw Oct 2000

Unit Secret Key

Entitlement Management Message or Unit Secret Key authorises specific decoders to decrypt the broadcast service, programme-by-programme if required.

Viewer Preference

During installation routines, the television set or set-top box allows the viewer to set the preferred mode for viewing non-compatible aspect ratios on the display.

Virtual Machine

A virtual machine is a software concept whereby applets and programmes can be written which are independent of the microprocessor they are run on, so called 'platform independence'. The virtual machine takes the unified 'bytecode' and interprets it for the particular hardware it is running on. This is particularly important for digital terrestrial television, where there will be a plurality of hardware from different manufacturers as techniques rapidly evolve.

VOD (Video on Demand)

The term that applies to a broadband service delivering video entertainment to subscribers from the service provider's server.

The first VOD trials were carried out by Time Warner in Florida in 1994. It looked good but was hopelessly uneconomic. Similar trials and similar findings emerged in the UK from experiments by BT in Essex and by a consortium in Cambridge.

Two smaller organisations have hung on in the UK, YesTV in Cardiff, which uses an NTL cable franchise and Video Networks, operating in a small area of North London nominated by BT for ADSL trials. Also, independent telco Kingston Telecommunications ran a trial with Yes TV in Beverly, covering 1500 households, until the telco decided it could do it on its own.

More recently, UK cable company Telewest launched one of the biggest trials in the world covering 27,000 households in Basildon, Essex. And Video Networks are now expanding into a commercial service called Home Choice to be offered wherever BT have rolled out ADSL.

The problem for independent operators is still the price charged by the telco for the broadband loop to the home. Services currently run at a loss but there is some confidence that the price will come down to the point where a viable business is possible. Its not for the faint-hearted. Service providers need good movies at or before they appear in video rental stores; deals with the Hollywood majors still havent really cracked the timing issue.

The other part of the service is on-demand replay of recent broadcasts—the programmes you forgot to record—and the ability to have stop / start / rewind on current broadcasts. Its a very similar service to that provided by PVRs. The issue is whether a remote service provider can do it bigger and better.

WebTV

The name of a Microsoft company specialising in putting Internet content onto viewer's television sets via a set-top box. It is becoming a general term. Traditional broadcasters had better watch out—if they don't embrace it, Microsoft and others will surely 'steal' the television set!

WebTV started life as a wayof displaying internet on a television set. The WebTV box has been sold to some 700,000 PSTN and cable customers in the USA, accessing WebTV's server to give general internet access on the TV. Internet pages are modified by the server on-the-fly to make them suitable for display on a low-resolution display.

The original system has been developed and WebTV now integrates with cable companies' services with a sophisticated EPG being downloaded overnight to a hard drive in the box. Microsoft are also supplying a similar system for Echostar in the USA. The cable company's television services cn be linked to downloaded data via commands transmitted in the VBI of the transmitted analogue signal.

With the advent of digital, Microsoft are, of course, keen to develop and have been active in the html task group of DVB-TAM (the technical committee of MHP). They point out that their system is compatible with the DSM-CC object carousel for over-air data and uses open standard html in the return path. They have a business interest in supplying "back-end" MCIS (Microsoft Customer Internet Services) servers and woul;d, of course, be delighted to supply their proprietary Windows CE for the set-top box, but it is not essential.

Clearly, Microsoft have an end-game streaming video programmes over broadband cable in competition with satellite and terrestrial. Recent investment in go-ahead cable companies secures them a foundation for when the broadband revolution happens. That might be sooner than we think!

(More: WebTV web site)

Widescreen

Widescreen television has an aspect ratio of 16x9. It is close to the golden ratio used by painters. Movies went widescreen in the 1950's but it is only recently that improving technology has made it possible to make a picture tube that shape.

The shape of all tv sets in the future, it makes for much better portrayal of feature films on tv. When flat-screen televisions become affordable, you really will be able to enjoy the home cinema experience.

XML (eXtensible Markup Language)

Like HTML, in which this web page is written, XML uses pairs of so-called tags to label (or mark-up) sections of text in order to specify how they will be used or shown. Unlike HTML, a user can define their own set of XML tags (known as a schema) for a particular purpose and as a result XML is being used as a kind of super-markup language in which specialised markups are defined. One example is SMIL (pronounced SMILE) which is a markup for synchronising time-based multimedia objects with each other and with more static things like text and web links.